Android Flaw Exposes DNS Queries Despite VPN Kill Switch

Several months ago, a Mullvad VPN user discovered that Android users have a serious privacy concern when using Mullvad VPN. Even with the Always-On VPN feature activated, which ensures that the VPN connection is always active, and with the “Block connections without VPN” setting active, which acts as a kill switch that ensures that only the VPN is the one that passes network traffic, it has been found that when switching between VPN servers, Android devices leak DNS queries. 

It is important to understand that enabling the “Block Connections Without VPN” option (also known as the kill switch) ensures that all network traffic and connections pass through an always-connected VPN tunnel, preventing prying eyes from tracking all Internet activity by users. During the investigation, Mullvad discovered that even with these features enabled in the latest version of Android (Android 14), a bug still leaks some DNS information. 

As a result, this bug may occur when you use apps that make direct calls to the getaddrinfo C function. The function provides protocol-independent translation from a text hostname to an IP address through the getaddrinfo function. When the VPN is active (and the DNS server is not configured) or when the VPN app re-configures the tunnel, crashes or is forced to stop, Android leaks DNS traffic. 

This leakage behaviour is not o

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